When — or if — cashless tolling starts on the 520 Bridge in December, it will be one of the most audacious things that’s ever happened to state transportation.

It’ll affect hundreds of thousands of people on the Eastside and Seattle.

It’ll put tolls on what’s now a free route across Lake Washington.

And if that’s not hard enough — making people pay for something they get for free now — there’s a vast mix of complications, including five types of vehicle transponders, tolls that range from zero at night to $5, depending on the time of day and payment type, and then making everything match.

“This project is among the most complex in the tolling industry,” is how an Expert Review Panel summed it up in an August report.

“The requirements they have established go beyond anything in place today. Implementing this system far exceeds the difficulties experienced by most toll agencies,” the panel added.

With a cost estimated at $4.65 billion, redoing the Highway 520 corridor, including the bridge, will be one of the most expensive road projects in history. The record is held by Boston’s “Big Dig,” put at $22 billion, but redoing I-90 from Seattle to Bellevue in the 1980s came to $1.46 billion and Seattle’s Alaskan Way Viaduct replacement is projected at $3.1 billion. About $1 billion of the 520 cost is to be paid through tolling.

Whether the 520 tolling will work is unknown. Tolling was supposed to start nearly a year ago, but the review panel, made up of six tolling-industry experts, found that schedule never was realistic.

And one panel member, Ron Fagan, who spent 14 years running Texas toll roads, has precisely described what can go wrong:

“You can lose a lot of money doing this if you don’t have the basics right — and there are certain critical operational aspects that you need to understand before you take the risk of just switching to all-electronic because that’s the sexy new thing,” Fagan wrote in explaining why he was going into private consulting.

At the same time, cashless tolling undeniably is foreseen as the way to move people in places as divergent as Australia, South Africa and Florida.

It also offers undeniable benefits: Drivers don’t even have to slow down to pay tolls, so choke points disappear. No expensive salaries have to be paid for toll collectors. Chances for human error are reduced. No huge piles of money have to be counted and physically handled.

Yet making the systems work to allow those benefits can be nearly overwhelming.

“You can’t get it wrong,” said Tyler Patterson, Washington State Department of Transportation toll operations engineer. “You bill the wrong people, and that shoots down the whole system.”

“My personal feeling is they’re trying to do too many things at once,” said Peter Samuel, a former newspaper reporter who’s found a niche as a toll-road expert through publishing a newsletter called TOLLROADSnews for the past 15 years.

In any case, the state DOT finds itself dealing with three tolling projects at once, on the Tacoma Narrows Bridge, Highway 167 in the Green River Valley and now 520.

At the least, just the technical work involves sorting out systems that would have seemed impossible a few years ago.

How tolling works

The basic concept for tolling 520, which carries over 100,000 vehicles a day, involves two types of charges.

One’s called “Good To Go.”

That’s induced more than 100,000 people to pay a minimum of $30 to buy “Good To Go” transponders, partly through clever TV ads.

The transponders themselves are something of a technological wonder.

They come in versions that can be mounted on places like a windshield or a license-plate holder and tests have shown they’ll even work if they’re stuck in a glove compartment.

They’ve even become so cheap that Samuel says it might soon be easier to give them away than charge for them; they used to cost about $25 each, but now they’re down to as low as $1.25 apiece.

And while once transponders were kind of clunky, box-like things, now they’re barely bigger than a credit card.

Even worries about issues like batteries are in the past.

Present-day transponders use something called “passive backscatter” for their power, meaning the signal that reads the transponder information also powers the transponder itself.

Drivers can see some indications of how the system will work just by driving across the bridge. The antennas and cameras and most of the other visible equipment to allow tolling has been installed on girders of the East High Rise, the transition section that leads from 520’s floating pontoons to land in Medina.

Even that was something of a compromise, said Patterson. When the 520 route opened in 1963, it had toll booths on land, just east of the bridge.

But the land there is virtually unusable for such installations now, he added, with nearly all of it torn up for construction. And putting the gear on the bridge itself, where it would be over water on pontoons, also wasn’t very desirable, leading to the temporary high-rise location.

All of it’s scheduled to be replaced when a new bridge is opened, now planned for 2014.

For all their golly-how-cool characteristics, however, the transponder concepts might be considered fairly straightforward.

The theory is that people establish an account and pay for a transponder, probably with a credit card, and when they cross the bridge, a signal is sent and a toll is deducted from their account. Get near the bottom of your money, and an autopay feature puts in more bucks.

In theory, almost nothing could be easier, and cashless toll systems routinely have 70 or 80 percent transponder use, notes Samuel, accounting for the bulk of traffic.

That still leaves thousands of non-transponder drivers, however, and that’s where cameras come in, allowing a license-plate recording system that makes up the heart of the system, matching vehicles and license plates and transponders.

Again, in theory, this isn’t too hard.

The cameras are made by a company called JAI and trace their origins to industrial systems developed in Denmark beginning in 1963.

Part of the technology actually stems from counting things like pop bottles, said Rich Dickerson, a JAI spokesman.

It turns out that JAI cameras are commonly used for chores like inspecting bottles on production lines, checking for things like whether caps are in place, whether the bottles are filled and labeling. That might make it seem like, compared to counting billions of bottles, keeping track of 100,000 cars a day on 520 would be easy.

That’s not quite the case, said Dickerson.

Counting cars on a bridge in a rainy December isn’t really much like counting beer bottles in a factory, said Dickerson.

“It’s a little bit more dynamic an environment,” he said.

It also turns out the key to the cameras isn’t really the cameras themselves, he explained, but the triggering mechanism.

While the cameras are certainly examples of advanced technology, shooting some 30 frames a second, compared to maybe five frames a second for a fancy amateur camera, they’re nowhere near 10,000-frames-a-second cameras that might be used to capture a speeding bullet.

They will record license plates on cars moving up to 150 mph, added Dickerson, but the real secret is finding the proper balance to make everything work.

For example, a constantly-running camera system wouldn’t be good, he noted, since it would generate too much information, which already is something of a problem.

“You’re pumping all this data into the network, you’re creating huge bottlenecks,” he said.

What’s better is a system that takes a picture when there’s something to photograph, like a car in a lane.

Yet even that’s not easy, added Dickerson. If a car is changing lanes, for example, a camera might record just half a license plate.

The way around that is to have enough cameras, and Patterson notes there’ll be 12 of them on 520, with three on each lane, two doing front plates and one for rear readings, for four lanes.

But there’s more.

The cameras have to work all day, of course, but they also have to work at night. And in rain, and snow.

Yet it’s obvious that the usual way people take pictures in the dark —with a flash — wouldn’t work on 520; imagine having someone set off a strobe light into your windshield at 60 mph.

The solution there is to use something invisible — but not an infrared camera, said Dickerson, since that often results in a “floating plate image,” meaning the license plate is visible, but not the vehicle, so the plate and the car can’t be matched.

Instead, what’s used is called “dual-band flash,” said Dickerson, or “near-infrared.”

The effect is to get something like a flashgun, but invisible.

“You want a wavelength that’s just outside human perception,” said Dickerson.

While this can be done, it’s also not exactly simple.

The state’s contractor “should research and test alternative options for night illumination if the near-infrared does not produce the quality required,” the Expert Review Panel concluded in August.

Such technical questions are just parts of many other procedures that have to be in place before tolling can start, however.

There’s a whole toll-collection system, allowing for the mailing of bills to non-transponder-equipped drivers, and arranging the ultimate sanction, of not allowing drivers with unpaid bills to renew their license tabs.

Provisions have to be made for rental cars and out-of-state drivers. An administrative-law-judge process has to be created, with the judges still to be hired, to deal with drivers who think they’ve been improperly billed.

This alone can be a source of bedeviling complexity, with a DOT audit noting a backlog of 100,000 tolling violations had been run up on the Tacoma Narrows Bridge by April, after a change of tolling contractors there.

Such work is part of what’s known as the “back office” of tolling, and that’s often seen as the real, and invisible, challenge to getting tolling on 520.

“That’s usually the bigger challenge,” said Dickerson.

In fact, both the Expert Review Panel and an internal DOT audit have cited such “back office” questions as critical.

Incidentally, the 520 “back office” is in Seattle’s University District. With an address of 4554 Ninth Ave. N.E., it’s where the state’s tolling contractor, Electronic Transaction Consultants, of Richardson, Tex., houses its operations here.

It’s the “back office” functions that have caused substantial problems, the Expert Review Panel found.

“The vendor’s lack of understanding of the accounting requirements has caused several missteps in development of the system,” the panel found.

The DOT internal audit was done on Tacoma Narrows procedures, since tolling isn’t yet used on 520, but also raised substantial doubts about proposed 520 operations.

“It will be important to address the recommendations above before beginning tolling on the 520 bridge, as the current traffic and revenue reconciliation effort does not appear reliable or scalable to the large volume of transactions expected for SR 520,” the audit concluded.

In effect, that means the state has “to make sure all the toll transactions are reported,” and that the transactions have to be “subject to vigorous testing procedures,” said Steve McKerney, DOT director of internal audit

In practice, this means all the cars and the money match, he added.

“It’s gathering trip data and making sure that results in a billed transaction,” said McKerney.

“The problem is really designing those standard reports and having the vendor develop the software,” he added.

As an example of what has to be done, McKerney explained that part of the work on the Tacoma Narrows Bridge, which handles about 40,000 vehicles a day and isn’t cashless, still using human toll collectors, routinely works with Excel spreadsheets to track transactions.

“That is a much more manual process,” he said, and it’s unlikely such techniques could be adopted for the fully automated 520 tolling.

McKerney said he didn’t know what type of programs or operating platforms would be used by ETC in meeting the 520 requirements, since the DOT audit function isn’t involved in designing programs.

ETC has had a mixed record of meeting such requirements. Besides encountering problems on the Tacoma Narrows Bridge, the corporation has been the subject of disputes in operations in Louisiana and Florida.

Yet the business also won a significant contract in August, getting an $88 million award from the Port Authority of New York and New Jersey to handle tolling on four bridges and two tunnels, carrying 242 million vehicles a year, dwarfing Washington State traffic.

ETC declines to discuss what problems it’s facing in making back-office functions work.

But Mark Hallenbeck, director of the University of Washington’s transportation research center, describes what’s essentially an accounting morass.

Whatever software is used, he explained, has to keep track of everything from expiring credit-card dates to matching cars and owners so bills can be mailed, involving tracking ownerships through 50 states and even internationally, perhaps to Canada or elsewhere.

“The lookup process is pretty ugly,” he said.

Then there are such questions as how to handle after-the-fact billing, since charges are sent after the bridge crossings.

“Do you send 20 bills?” if the crossings are made over a period of days, he asked. “Here’s where the reconciliation process gets difficult.”

Such questions are simple and obvious issues compared to what’s really involved, he added.

“Details of how you track this internally are 16 times more difficult,” he said.

“The problem is internal software, and it’s cascading downwards,” he said. “It’s going to take longer and cost more than we ever anticipated.”

It’s an Oracle-based database that’s being used to track the information, said Patty Rubstello, DOT’s director of toll systems development and engineering, with data then imported into another tool.

“We’re plugging along,” said Rubstello, who explained that she can’t specifically comment on the reconciliation progress.

Whether ETC can meet the December schedule hasn’t been resolved, of course, and the deadline really is earlier, with 30 days or more of successful testing needed before tolling begins.

“During the last week of this process, nearly every user of SR520 should be identified and determination made as to any additional support needed for the go-live period,” concluded the Expert Review Panel.

In August, DOT announced it was focusing on meeting audit reporting standards and other requirements.

“We’re also planning for several weeks of testing that will start after those reports are refined, followed by a final month of testing that will serve as a dress rehearsal,” said Craig Stone, DOT Toll Division director.

If, somehow, it doesn’t all work out by December, the Expert Review Panel also had some other words of advice.

“Recognize the worst-case issues … and develop corrective actions to take if they are experienced,” the panel recommended. “Anticipate the need to operate more of the system without vendor support and know what is needed to accomplish this.”